Significance of seismites in the Late Cretaceous transgressive Nimar Sandstone succession, Son-Narmada rift valley, Central India

Abstract

Detailed facies architecture study of the Late Cretaceous (Cenomanian) Nimar Sandstone (Bagh Group), from Son‐Narmada rift valley, Central India, reveals deposition in a fluvial–marine environment. The lower part of the Nimar Sandstone succession depicts deposition in predominantly fluvial setting, whereas the middle–upper part of the succession manifests sedimentation under a tide‐dominated estuarine to a tide–wave influenced shoreface environment. Retrogradational nature of the successions in the upper part and lateral facies change from west to east signifies an eastwardly decreasing marine influence. This attests to a sustained event of marine transgression from the west affecting the Son‐Narmada rift valley during the Late Cretaceous time. Beds with various soft‐sediment deformation structures (SSDS), viz., convolute laminae, load and flame structures, pseudonodules, contorted beddings, syn‐sedimentary faults, and sand/silt dykes, occur in distinct stratigraphic levels within the middle part of the succession. These beds are separated by thick successions of undeformed beds. This paper reports these beds as seismites for the first time from the Son‐Narmada rift valley. The seismites signify instantaneous liquefaction and fluidization of unconsolidated sediments triggered by passage of repetitive earthquake shock waves during sedimentation in fault‐bound rift basin. These seismites are important as they mark a new phase of reactivation of the Son‐Narmada South Fault within the Son‐Narmada rift valley during the Cenomanian time. This reactivation of the Son‐Narmada South Fault led to basinal subsidence under prevalent extensional tectonism, which controlled the sedimentation during the Late Cretaceous time. Copyright © 2016 John Wiley & Sons, Ltd.

Palaeogeographic reconstruction of a fluvio-marine transitional system in Narmada rift basin, India — Implications on Late Cretaceous global sea-level rise

“…Such repetitive fining-up cycles indicate the inundation of fluvio-tidal channels by marine waters within a typical estuarine setting (Nichols 2009). In the study area, overall dominance of tidal features over wave features points to a tide-dominated waveinfluenced estuary (Jha et al 2017).…”

“…Large-scale trough cross-strata with lateral accretion and mud-draped foresets indicate migration of bars by tidal currents (Bose and Das 1986); convolute laminae indicate liquefaction and fluidization during deposition (Jha et al 2017).…”

“…Mutually opposite cross-strata set indicate tidal fluctuations (Klein 1971;Boersma and Terwindt 1981;Elliott 1986); symmetrical ripples and combined flow ripples manifest interference of tides and waves; wavy and lenticular beddings indicate pronounced suspension fall-out over alternate traction current; alternation of laminated sandstone-mudstone indicates tidal inclined heterolithic strata (IHS) in lowenergy tidal setting Wunderlich 1967, 1969;Reineck and Singh 1980;Choi et al 2004;Choi 2010). Suspension deposit during slack phase (Reineck and Singh 1980); SSDS indicates density contrast among the litho-units during deposition (Jha et al 2017).…”

“…Coarse grain size and symmetrical ripples with chevron laminae indicate moderate-energy wave conditions (Harms et al 1975). At different stratigraphic levels in the middle part of the studied succession, layers with various soft-sediment deformation structures (SSDS), e.g., convoluted laminae, pseudo-nodules, load and flame structures, synsedimentary faults, slumps, and sand dykes, have been recorded by Jha et al (2017).…”

“…The Nimar Sandstone (Cenomanian) Formation, the lowermost litho-unit within the Bagh Group (Late Cretaceous), bears signatures of the contemporary global sea-level rise in west-central India (Jha et al 2017). Signatures of the Late Cretaceous marine transgression in the Bagh Group are evident and agreed well in terms of different proxies such as sedimentary attributes, palaeontological data, ichnological data, micropalaeontological data and palaeobotanical data (Murty et al 1963;Chiplonkar and Ghare 1975;Raiverman 1975;Badve and Ghare 1980;Singh and Srivastava 1981;Jafar 1982;Bose and Das 1986;Ganguly and Bardhan 1993;Sanganwar and Kundal 1997;Khosla et al 2003;Smith 2010; Jaitly and Ajane 2013; Bhattacharya and Jha 2014;Jha et al 2017;Bansal et al 2019; and many others). But, a comprehensive sequence stratigraphic model enumerating the actual nature of coastal onlap and the fluvial-marine interaction has not been attempted and is long overdue.…”